Radio Aids to Navigation (RAN) becomes much closer in our social life and yet it cannot possibly be replaced, its convenience and safety fully guaranteed by successful application of radio waves, are beginning to be influenced seriously by the recent electromagnetic environment.In this studying, we have discussed about under-mentioned results.1) In the first, a review of the progress of historical research of radio wave application and its assignment was discussed, and the problems of electromagnetic compatibility in the GPS, the hyperbolic, and radar navigation, are also outlined.2) In the second, the disturbance problems of LF band waves caused by bridges built according to the social development program are discussed. According to these results, a couple of high bridge-towers could be considered to be vertical electric dipole antennas. Hence, it is possible to establish an antenna model of the bridge consisting of two parallel vertical electric dipole antennas with 0.2*F static capacitance in each.3) In the third, a series of phase errors measurement of 8930 Loran-C chain was made, using both rho-rho Loran-C receivers and RTK-GPS/OTF in the summer of 1997. It is shown that some aspects of the experimental results are reasonably interpreted by using the models of considering both a couple of vertical towers and the metallic materials to be vertical electric dipole antennas.4) In the fourth, the phase error is discussed with relation to the incident angle. It is found that at angle of 45ﾟthe reflection from the coastline appears to be very weak and the reflection strong at highly oblique incidence. As the usual ship-borne Loran-C receiver indicates time difference in units of 0.1 *S, the region where the phase error becomes larger than *0.1 *S is considered to be significantly affected by the reflected wave from the coast. These distances from the coastline are as follows : about 2km for near normal incidence, 300m for 45ﾟ, and more than several km for 60ﾟ - 75ﾟ.